Does excessive junk food consumption change the way the brain reward system processes intrinsic rewards?

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The prevalence of obesity worldwide continues to increase dramatically: 39% of adults are now overweight or obese. Excessive consumption of highly palatable sugar and fat laden foods, often referred to as “junk foods”, plays a central role in the development of obesity, possibly by dysregulating the brain reward system. The REBOST project aims to investigate the neurological mechanisms by which excessive junk food consumption adversely affects the reward system. I hypothesise that excessive junk food consumption desensitises the reward system, which alters responses to different intrinsic rewards. This project is innovative in that it investigates the neuronal and behavioural alterations in sensitivity to rewards beyond conditioned food rewards, by also studying the responses towards a secondary intrinsic (sexual) reward. This will be achieved by using a unique behavioural design and advanced in vivo techniques (fibre photometry, dLight1 and chemogenetics). This protocol allows to simultaneously investigate real-time neuronal activation and behavioural effects during all distinct phases of reward: i) expectation, ii) approach and iii) consummatory behaviour. Another highlight of the project is the use of the Cafeteria Diet model (CAF). CAF mimics human behaviour more accurately than other models, by feeding rats a choice of the same unhealthy, but palatable products as humans. By integrating complementary expertise on CAF and food reward from the ER and on sexual behaviour and the advanced techniques from the host, the project will unravel the effects of CAF on the specific brain reward projections from the Prefrontal Cortex to the Ventral Tegmental Area. This will contribute to explain the underlying mechanisms of the development of obesity and the vulnerability of the brain reward system, which will open up new strategies for biomedical research and therapeutic applications, both for obesity and addiction.